Service provider networks may include computer networking infrastructure, or a “backbone,” through which one or more customers may communicate and establish logical, or “virtual,” networks. Data are often transmitted over such networks in suitably-sized packets, regardless of the data type. This is known as packet switching. Customers who wish to establish sustained logical networks on a service provider network may utilize virtual circuit switching, also known as connection-oriented switching. Examples of virtual circuit switching protocols include multiprotocol label switching (“MPLS”) and asynchronous transfer mode (“ATM”).
An exemplary service provider network 10 is shown in FIG. 1. Service provider network 10 includes core infrastructure 12 (referred to as “MPLS CORE” in FIG. 1) that includes one or more intermediate routers 14 and one or more provider edge (“PE”) routers 16. Each PE router 16 may connect to one or more customer edge (“CE”) routers 18. Customers who wish to utilize service provider network 10 may do so through a CE router 18.
A virtual private network (“VPN”) is a logical network that is overlaid on an underlying computer network and that provides a way for users of the VPN (referred to herein as “customers”) to communicate without interfering with other network traffic. A VPN may be secure, which means customers may communicate with each other over the VPN confidentially. A VPN also may be trusted, which means the VPN is used for traffic segmentation between various customer sites connected to a service provider network. Trusted VPNs may provide quality of service (“QoS”) guarantees and other features to customers. A VPN customer need not be aware of the structure of the underlying service provider network. In FIG. 1, two VPNs called “VPN BLUE” and “VPN RED” are implemented on service provider network 10.
One type of VPN is a so-called “Layer 3” VPN (“L3VPN”). Two exemplary L3VPNs, BLUE VPN and RED VPN, can be seen in FIG. 1 by observing that BLUE VPN and RED VPN sites are shown connected to the service provider network via the CE routers. These VPNs may be implemented using various technologies or combinations thereof, including but not limited to MPLS, the Border Gateway Protocol (BGP”) and Multiprotocol BGP (“MP-BGP”), which is an extension of BGP. PE routers may exchange VPN route prefixes using BGP. A PE router may identify as peers other PE routers with which the PE router exchanges VPN route prefixes.
Total failure of a network element (e.g., loss of power, hardware failure) may not be detectable until after-the-fact, which may delay significantly a determination of the failure's effect on services of a VPN. Sometimes, however, a network element may not experience total failure, but a software communication process on the element may experience failure that nonetheless affects VPNs and VPN services.
For example, a BGP communication process executing on a PE router may experience a failure. Such software failure may have various causes, such as buffer overflow or insufficient memory. Although the PE router is still up and running, VPN sites connected to the PE router, including CE routers, may experience degradation in performance or even total loss of connectivity. Without being able to detect such a protocol failure, a network administrator may have difficulty diagnosing a root cause of the failure or responding to the problem quickly enough to avoid customer complaints.